1. Field of the Invention
A following description relates to an apparatus and method for offsetting a transmission leakage signal of a radio frequency identification (RFID) reader, and more particularly, to an apparatus and method for offsetting a transmission leakage signal of an RFID reader, the apparatus and method which offset the transmission leakage signal by applying the transmission leakage signal of the RFID reader to an injection lock oscillator (ILO).
2. Description of the Related Art
In regard to a transmission signal of a conventional radio frequency identification (RFID) reader, a transmission leakage signal transmitted from a transmitter of the RFID reader flows into a receiver of the RFID reader.
The transmission leakage signal flown into the receiver reduces reception sensitivity of the RFID reader. Generally in RFID communication, a tag operates by an extremely low power and a power level of an RF signal received from the tag is extremely low. However, a power level of the transmission leakage signal flowing from the transmitter to the receiver of the RFID reader is relatively higher than a power level of a received power from the tag. The transmission leakage signal becomes a main factor that reduces a signal to noise ratio (SNR) of the receiver of the RFID reader.
According to a generally used method to solve the SNR reduction, amplitude and a phase of the transmission leakage signal are measured and a signal having an opposite phase and equal amplitude are generated to combine with and offset the transmission leakage signal. However, in the RFID reader, the amplitude and the phase of the transmission leakage signal are not constant but often changed due to external circumstances of an antenna connected with the RFID reader.
Accordingly, there is a demand for a separate device for measuring amplitude and a phase of a transmission leakage signal, which are changeable, and an additional control device for changing the amplitude and phase according to the measured values.